Hoping that a Dell motherboard will overclock is like hoping it will rain money. Ain't gonna happen. The only Dell I ever knew to overclock was my old PPro that had an unmarked jumper that took it from a 200 to a 233.
If you want to flhas your Dell board with a non-Dell BIOS, why not just send the system to me instead, since either way you'll be out a motherboard.
Pete